The Spartan Warrior

The truth about fitness and nutrition.

Calculating Calories and Macronutrients

Basic Terminology

  1. BMR (Basal Metabolic Rate): This is the amount of calories you need to consume to maintain your body if you were comatose (base level)….
  2. NEAT (Non-Exercise Associated Thermogenesis): The calorie requirements added by your daily activity that is NOT exercise (eg: washing, walking, talking, shopping, working). This is generally the most marked variable in a persons daily calorie requirements and something that everyone has a good amount of control over. This is what people term INCIDENTAL EXERCISE. It is also what helps keep ‘constitutionally lean’ people LEAN (they fidget)!
  3. EAT (Exercise Associated Thermogenesis): The calorie requirements associated with planned exercise…. Unless someone is doing a whole heap of exercise (eg: two or more hrs training a day) it usually doesn’t add a stack of calories to your requirements (30 minutes of ‘elliptical training isn’t going to do it’)
  4. TEF (Thermogenic effect of feeding): The calorie expenditure associated with eating…. REGARDLESS of what myths you have been told - this is NOT dependent on MEAL FREQUENCY. It is a % of TOTAL CALORIES CONSUMED (and 15% of 3 x 600 cal meals is the same as 15% of 6 x 300 cal meals). It varies according to MACRONUTRIENT content and FIBER content… For most mixed diets, it is something around 15%…. Protein is higher (up to 25%), carbs are variable (between 5-25%), and fats are low (usually less than 5%). So -» More protein and more carbs and more fiber = HIGHER TEF. More FAT = LOWER TEF.
  5. TEE (Total Energy Expenditure): The total calories you require - and the sum of the above (BMR + NEAT + EAT + TEF).

How much do you need?

There is therefore a multitude of things that impact a persons MAINTENANCE calorie requirements

  • Age and sex (males generally need > females for any given age)
  • Total weight and lean mass (more lean mass = more needed)
  • Physiological status (eg: sick or injured, pregnant, growth and ‘enhancement’)
  • Hormones (eg: thyroid hormone levels, growth hormone levels)
  • Exercise level (more activity = more needed)
  • Daily activity level (more activity = more needed)
  • Diet (that is - macronutrient intake)

In order to calculate your requirements the most accurate measure would be via Calorimetry [the measure of ‘chemical reactions’ in your body and the heat produced by these reactions], either directly (via placing a calorimeter where the heat you produce is measured) or indirectly (eg: HOOD studies where they monitor how much oxygen you use/ carbon dioxide and nitrogen you excrete over a given time). Although accurate - this is completely impractical for most people. So we mostly rely on pre-set formula to try to calculate our needs.

Read more to see how to estimate your requirements and get the right macro-nutrients in your diet.

Estimating Requirements

The simplest method of estimating needs is to base your intake on a standard ‘calories per unit of weight (usually kilograms)’. Typically:

  • 26 to 30 kcals/kg/day for normal, healthy individuals with sedentary lifestyles doing little physical activity [12.0-14 kcal/pound]
  • 31 to 37 kcal/kg/day for those involved in light to moderate activity 3-5 x a week with moderately active lifestyles [14-16 kcal/ pound]
  • 38 to 40 kcals/kg/day for those involved in vigorous activity and highly active jobs [16-18 kcal/ pound].
  • For those involved in HEAVY training (eg: athletes) - the demand is even greater:
  • 41 to 50 kcals/kg/day for those involved in moderate to heavy training (for example: 15-20 hrs/ week training) [18.5-22 kcal/ pound]
  • 50 or above kcals/kg/day for those involved in heavy to extreme training [> 22 kcal/ pound]

Then a number of more complex formula which calculate BMR can also be used - which is then multiplied by an ‘activity variable’ to give TEE.

To go over a few BMR calculations:

    1. Harris-Benedict formula:

Particularly inaccurate - It was derived from studies on LEAN, YOUNG, ACTIVE males in a COLD lab MANY YEARS AGO (1919) and is notorious for OVERESTIMATING calorie requirements, especially in those that are overweight. IF YOU WANT AN ACCURATE READING, DON’T USE IT!

  • For MEN: BMR = 66 + [13.7 x weight (kg)] + [5 x height (cm)] - [6.76 x age (years)]
  • For WOMEN: BMR = 655 + [9.6 x weight (kg)] + [1.8 x height (cm)] - [4.7 x age (years)]

     2. Mifflin-St Jeor:

Developed in the 1990s. More accurate than the above as it is more realistic in todays lifestyle settings. It still does not take into consideration the difference in metabolic rate as a consequence of high BF%. Thus, once again, it also overestimates needs in highly obese individuals. So - be warned it can OVERESTIMATE your needs.

  • For MEN: BMR = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] + 5
  • For WOMEN: BMR = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] -161

     3. Katch-McArdle:

This is considered the most accurate formula for those who are relatively lean and who have a good understanding of their bodyfat %.

  • BMR = 370 + (21.6 x LBM)
  • Where LBM = [total weight (kg) x (100 - bodyfat %)]/100

To convert to a TOTAL requirement you multiply the result by an Activity Factor. THIS IS BASED ON MORE THAN JUST YOUR TRAINING! Your job/ lifestyle is important in this!

  • 1.2 = Sedentary (Little or no exercise and desk job)
  • 1.3-1.4 = Lightly Active (Little daily activity & light exercise 1-3 days a week)
  • 1.5-1.6 = Moderately Active (Moderately active daily life & Moderate exercise 3-5 days a week)
  • 1.7-1.8 = Very Active (Physically demanding lifestyle & Hard exercise or sports 6-7 days a week)
  • 1.9-2.0 = Extremely Active (Hard daily exercise or sports and physical job)
  • (note: these activity factors generally include your LIFESTYLE (work) as well as your EXERCISE (gym/ sport) and a TEF of ~ 15% - which is an average mixed diet).

How Accurate are they?

Although these (sometimes) give rough ball-park figures, they are still ‘guesstimations’. Most people still OVERESTIMATE activity, and UNDERESTIMATE bodyfat & end up eating TOO MUCH. So - use these as ‘rough figures’ and monitor your weight/ measurements for 2-4 weeks. IF your weight is stable/ measurements are stable, then you have likely found maintenance.

Using the Above to Recalculate Based on Goals

You will need to DECREASE or INCREASE intake based on your goals (eg: lose or gain mass).

And instead of using ‘generic calorie amounts’ (eg: 500 cals/ day), this is calculated on a % of your maintenance. Why? The effect of a given calorie amount on an individual is going to be markedly different based on their size/ total calorie intake. For example - subtracting 500 cals/ day from a 115# females 1500 total intake is 1/3rd of her total cals but 500 cals/ day for a 215# male on 3500 total intake is only 1/6th of their total… And it will result in markedly different effects on their energy levels and weight loss.


  • to ADD weight: ADD 10-20% calories to your total from above
  • to LOSE weight: SUBTRACT 10-20% calories from your total from above

Then monitor your results and adjust as required.


There is an energy cost associated with growth / inefficient movement / high surface area:mass ratio. Look HERE for alternatives.
As a teenager I would also STRONGLY suggest you don’t obsess on calories and macros! Eat well, exercise regularly, and have fun while you can!

Macronutrient Needs

Once you work out how many CALORIES you need you need to work out how much of each macronutrient you should aim for. This is one of the areas that is MOST often confused - so to try to make it as simple as possible:
First rule: This should NOT be based on a generic RATIO of total calorie intake such as ‘30:40:30 or 40:40:20 Your body doesn’t CARE what % intake you have for macronutrients. It works in terms of SUFFICIENT QUANTITY per LEAN MASS or TOTAL MASS. And calculations are generally as follows:

    1. Protein: Most studies out suggest that in the face of ADEQUATE calories and CARBS then the following protein intakes are sufficient:

  • STRENGTH training -> 1.2 to 1.6g per KG bodyweight (about .6 / pound)
  • ENDURANCE training -> 1.4 to 1.8g per KG bodyweight (about .8 / pound)
  • ADOLESCENT in training -> 1.8 to 2.2g per KG bodyweight (about 1g / pound)

BUT they also acknowledge that protein becomes MORE important in the context of LOWER calorie intakes, or LOWER carb intakes.

Anyway - you can see that the general recommendations given in the ‘bodybuilding’ area (1g / pound) is nearly double this! And although the evidence out to suggest a NEED for this requirement is scarce - some general ‘bodybuilding’ guidelines would be based as follows:

  • If bodyfat UNKNOWN but AVERAGE = 1-1.25g per pound weight
  • If bodyfat KNOWN = 1.25-1.5g per LEAN weight

If you are VERY LEAN or if you are on a LOW TOTAL CALORIE INTAKE then protein becomes more important - so stick toward the higher levels:

  • Average bodyfat, lower calorie intake = 1.25-1.5 x pound total mass
  • Bodyfat known, lower calorie intake = 1.33-2 x pounds lean mass

If you are VERY OVERWEIGHT, VERY INACTIVE, and NOT on a lower calorie diet then you should stick closer to, or decrease slightly BELOW the above levels:
protein = something around the 1 x total weight (down to 1 x LEAN MASS).

    2. Fats: Generally speaking, although the body can get away with short periods of very low fat, in the long run your body NEEDS fat to maintain general health, satiety, and sanity. Additionally - any form of high intensity training will benefit from a ‘fat buffer’ in your diet - which acts to control free radical damage and inflammation.

General guides:

  • Average or lean: 1 - 2g fat/ kg body weight [between 0.45 - 1g total weight/ pounds]
  • High bodyfat: 1-2g fat/ LEAN weight [between 0.45 - 1g LEAN weight/ pounds]
  • IF low calorie dieting - you can decrease further, but as a minimum, I would not suggest LESS than about 0.35g/ pound.

Note 1: Total fat intake is NOT the same as ‘essential fats’ (essential fats are specific TYPES of fats that are INCLUDED in your total fat intake)…

    3. Carbs: VERY important for athletes, HIGHLY ACTIVE individuals, or those trying to GAIN MASS - Carbs help with workout intensity, health, and satiety (and sanity). But there are no specific ‘requirements’ for your body. Carbs are basically used by most as ‘the extra stuff’.

If you are an athlete - I would actually suggest you CALCULATE a requirement for these:

  • moderately active: 4.5 - 6.5 g/ kg (about 2 - 3g/ pound)
  • highly active: 6.5 - 9 g/ kg (about 3 - 4g/ pound)

But for ‘general folk’ to calculate your carbs you just calculate it from the calories left over from fats/ protein:

  1. carb calories = Total calorie needs - ([protein grams as above x 4] + [fat grams as above x 9])]
  2. carbs in grams = above total/ 4

How do I count Calories accurately? Calorie Counting Websites

What are Macronutrients and Micronutrients? Macro and micronutrients explained!

(via Emma-Leigh)


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